This paper presents a design and analysis of an electromagnetic micro generator which can convert low frequency vibration energy to electrical power. The design aspects of the micro generator comprised planar spring, Cu coil and a permanent magnet(NdFeB). Threetype spring designs and four materials(Parylene, FR-4, Cu and Si) were compared to find resonance frequency. It was found that the resonance frequency will be changed according to the spring shape and material. Mechanical and magnetic parameters had been adjusted to optimize the output power through a comprehensive theoretical study.